1. Field of the Invention
The present invention relates to an organic light-emitting display and, more particularly, to an active matrix organic light-emitting display.
2. Description of the Related Art
Generally, an organic light-emitting display, which is an emissive display device that electrically excites a fluorescent organic compound to emit light, is classified into a passive matrix display and an active matrix display depending on a method of driving N×M pixels arranged in a matrix form, where the active matrix organic light-emitting display has lower power consumption than the passive matrix organic light-emitting display so that it is appropriate to implement a large area and high resolution display.
FIG. 1 is a cross-sectional view for illustrating a conventional active matrix organic light-emitting display and a method of fabricating the same, in which only a unit pixel is shown.
Referring to FIG. 1, a buffer layer 105 is formed on a substrate 100. A thin film transistor (TFT) including an active layer 110, a gate insulating layer 120, a gate electrode 130, an interlayer 140 and source/drain electrodes 145 is formed on the buffer layer 105 of the substrate 100 by the typical method. A via-hole insulating layer 155 is formed on the entire surface of the substrate, and a via-hole 150 that exposes one of the source/drain electrodes 145 is formed in the via-hole insulating layer 155.
Next, a pixel electrode 170 that contacts with the source/drain electrode 145 exposed in the via-hole 150 is formed. Here, since the pixel electrode 170 is formed along the bottom and sidewall of the via-hole 150, it has a bent shape in the via-hole 150. Subsequently, a pixel defining layer 175 is formed that covers the pixel electrode 170 bent in the via-hole 150, wherein the pixel defining layer 175 is formed to have an opening 178 that exposes the pixel electrode 170 at a place spaced from the via-hole 150. Further, an organic emission layer 180 is formed on the pixel electrode 170 exposed in the opening 178, and a second electrode (i.e., an opposite electrode) 190 is formed on the organic emission layer 180.
In the case of forming the organic emission layer 180, the organic emission layer 180 is vulnerable to failure of layer formation at the edge of the bottom of the opening 178, that is, at the portion P where the pixel defining layer 175 and the pixel electrode 170 meet. This can cause deterioration of the organic emission layer 180, in driving the organic light-emitting display. Further, the organic emission layer 180 contacts with the pixel defining layer 175 at the edge of the opening 178. Generally, the pixel defining layer 175 is formed of an organic layer, wherein the organic layer is known to outgas at a high temperature. The outgassing can cause deterioration of the organic emission layer 180 in contact with the pixel defining layer 175.
FIG. 2 is a picture showing a failure occurred in an organic light-emitting display.
Referring to FIG. 2, due to the foregoing problems, it can be found that the organic emission layer is deteriorated along with the edge of the opening (b) located at the unit pixel region (a). This is also referred to as ‘pixel shrinkage’. This significantly affects the yield of the organic light-emitting display.